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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y A SUGGESTED FORM OF VISCOSIMETER B y W. C. COPE Received July 21. 1917
T h e usual form of viscosimeter is based on t h e proposition of passing a given quantity of oil or other liquid contained in a cylindrical vessel a t a specified t e m perature through a n orifice of definite dimensions in a variable length of time. The viscosity of t h e liquid under examination, then, is obtained b y comparing t h e time taken for passing a like volume of liquid, such as rape seed oil, through t h e orifice under similar conditions. A criticism of instruments of this kind is: (I) t h e height of column of liquid is variable and t h e first half of t h e liquid collected comes through in less time t h a n t h e second half due t o less head of liquid in t h e viscosimeter; ( 2 ) a n oil of t h e nature and consistency of engine oil a t ordinary laboratory temperature will flow only a few cubic centimeters per minute (to get a n y d a t a on such a n oil t h e temperature must be raised and this will not indicate t h e viscosity at t h e lower temperature) ; (3) time may not be t h e proper medium for a basis of comparison.
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cone. A tachometer would indicate t h e speed a t a n y time. Temperature of test could be controlled b y carrying out t h e operation in a constant temperature room or enclosing t h e centrifuge in a case in which t h e temperature could be regulated, I t seems t o be impossible t o arrive a t any definite agreement as t o a standard instrument for viscosity while using t h e present system of time variation. It is believed t h a t a n agreement could be h a d on some modification of t h e principle suggested. The suggested form of apparatus is offered with t h e hope t h a t i t will raise discussion a n d accelerate investigation leading t o t h e adoption of a standard viscosimeter. E. I. DU FONT DE NEMOURS & COMPANY EASTERN LABORATORY. CHESTER, PA.
A CONVENlENT AUTOMATIC DEVICE FOR RAPIDLY WASHING PIPETTES B y AUBREY.VAIL FULLER Received September 11. 1917
A suggested form of viscosimeter which is shown in t h e accompanying drawing is based on a different principle and is therefore not subject t o t h e above criticism. It is described as follows: a n a r m of a centrifuge holds a cylindrical or other shaped cup having a n orifice of definite dimensions which is closed by means of a cone needle valve actuated b y a spring. A receiver is a t tached t o t h e cup t o retain any liquid passing through t h e orifice. The receiver is easily detached from t h e cup a n d b y reason of its flat bottom will be perfectly stable when placed on a balance pan. A definite quantity of oil or other liquid under examination is placed in t h e cup a n d t h e centrifuge is whizzed a t t h e desired speed when t h e valve is raised b y passing electric current through a solenoid which excites t h e soft iron core attached t o t h e valve. After a given time t h e current is shut off, whereupon t h e valve is closed b y t h e spring. A definite quantity of liquid will pass through t h e orifice in a definite period of time by varying t h e speed. Hence i t is seen t h a t temperature, time, and volume are constant and force variable. Knowing t h e length of t h e centrifuge a r m and t h e speed of rotation, t h e force required t o pass t h e liquid may be easily calculated b y t h e well-known formula. Viscosity, then, would be measured in terms of acceleration due t o gravity ( g ) , which is a rational system. The centrifuge could be driven b y a motor a n d t h e speed varied by means of a variable speed countershaft
Without doubt t h e piece of glass apparatus in daily use in quantitative analytical work most difficult t o cleanse thoroughly is t h e ordinary transfer pipette. I n order t o surmount these difficulties a n d t o render t h e ppocedure simpler and less time-consuming t h e writer has devised t h e automatic washing apparatus pictured. A is t h e inlet tube, which is connected with t h e water supply either by means of rubber tubing or by being B , B are t h e pipette permanently piped thereto. carriers, provided a t their enlarged ends with short These stoprubber stoppers bored with 3 / ~ - i n holes. . pers are fitted on their lower faces with gate valves C,C, made by cementing small squares of sheet rubber t o t h e m so as t o form a flap over t h e holes, t h e function of these valves being t o prevent t h e escape of water from t h e carrier not in actual use. D is a syphon a n d E a breather pipe, permitting t h e escape of air which would otherwise be compressed as t h e water rises in t h e carriers. The entire pipe system is supported in a copper-lined wooden t a n k , F , provided with a n outlet, G. The operation of t h e device is as follows: The supply t a p is opened until water flows from t h e syphon intermittently as in t h e familiar Soxhlet apparatus. The pipette t o be washed is then placed tip-up in one of t h e carriers. Water rises in both pipette and syphon, b u t on encountering t h e constriction a t t h e tip of t h e former, has its flow arrested, while i t freely rises t o t h e bend in t h e latter and syphonsout,emptying t h e pipette. T h e process repeats itself indefinitely, and one, or several pipettes of different sizes, may be washed simultaneously a n d without attention. I n a two-carrier apparatus as illustrated, a 5 cc. and a zoo CC. instrument may be washed side b y side. The cross-section of t h e syphon pipe is determined
